Frequency changer



Aug. 14, 1923.

C. LE G. FORTESCUE FREQUENCY CHANGER 'F'iled Sent. 19. 1919 INVENTOR I Char/es L 6'6! fa'r/Zsaue 1 w lT uEssesy faww ATTORNEY Patented Aug. 14, 1923.

V UNITED STATES PENNSYLVANIA.

. FREQUENCY CHANGER.

Application filed September To all whom it may concern Be it known that I, CHARLES Li; G. FoRTnsoUn, a subject of the King of Great Britain, and a resident of Pittsburgh, in the county of Allegheny and State of Pennsylvania, have invented a new and useful Improvement in Frequency Changers, of which the following is a specification.

My invention relates to frequency changers of the commutator type, such, for. example, as shown in U. S. Patent 682,943, issued to the lvestinghouse Electric & Mann, facturing Company on Sept. 17, 1 901, on an application filed by B. G. Lamme, and it has for its object to provide apparatus of the character designated that shall commutate in a more effective manner.

In the accompanying drawing, Fig. 1 is a circuit diagram of a machine embodying a preferred form of my invention, and Fig. 2 is a side view, partially in section and partially in elevation, of the machine of Fig. 1.

Frequency-changers are" well-known wherein an armature. is provided with a commutator and with slip rings and wherein one circuit is connected to the brushes of'the' commutator and the other to the slip rings. By driving this armature at various speeds and by supplying current of given frequency, as to the slip rings, currents of various frequencies may be taken from the brushes of the commutator. Apparatus of this character, however, has been subject to the disadvantage that. the commutation was rather poor. r I find that by placing an auxiliaryv dis tributed winding on the armature, with a commutator associated therewith, and by supplying current from the 'output mains to this auxiliary commutator through brushes in electrical quadrature to the main brushes, :1 fieldmay be developed in the armature which will radically improve the commutation.

Referring to the drawing for amore detailed understanding .of my invention, I show an armature at 5 driven from an. auxiliary variable-speedqmotor 6 through a shaft 7. The armature 5 is provided with a main winding 8 connected, on the one hand, to thesegments of afcommutator 9 and, on the other hand, to slip rings 10. The armature 5 is further provided with an 19, 1919. Serial No. 324,825.

auxiliary distributed winding 11 connected to the segments of a commutator 12.

Suitable brushes 13 1 0 and are connected to supply mains 14. cnergized'by single-phase current of the supply frequency. Main brushes 1515 bear on the commutator 9 and are connected to the load circuit 16-16 to ply the generated frequency. 7

The armature 5 is driven, at any desired speed,-by the shaft 7 from the motor 6 so that current is produced in the mains 16-16 of different frequency from that which is supplied through the mains 14: but with a tendency to defective commutation at the brushes 15-45.

In order to overcome this difficulty, the auxiliary brushes 17-17 bear on the auxiliary commutator 12 in electrical quad rature to the brushes 15-15 and are connected, respectively, to these main brushes, so that alternating current of the generated frequency flows through the distributed winding 11 and produces alternating flow therein in quadrature to the brushes 15-15. The cutting of this field by theshort-circuited armature coils undergoing commutation produces such electromotive force therein as to radically improve the commutation and, furthermore, this improvement is suitable in nature, under varying conditions of load and with varying output frequencics, since the frequency of the current producing the alternating-current field is the output'frequency of the machine.

Referring to Fig. 2, one. structural arrangement of the apparatus of Fig. 1 is shown, the main commutator 9 being mounted at one end of the armature 5 and the auxiliary commutator 12 being placed at the other 1010.

end thereof, within the slip rings bear on the slip rings which it is desired to sup-, l

In o'rderto complete the magnetic circuit of the armature, a field member 18 is dis posed the'rearound. If the armature .5 is not self-driving, have no winding and may actually rotate with the armature, as is well known with machines ofthis type.

WVhile I have shown my invention in its preferred form, it will be obvious to those skilled in the art that it is not so limited but is susceptible ofvarious minor changes the field member 18 need and modifications without departing from the spirit thereof and I desire. theretor that only such limitations shall. be placed thereupon as are imposed by the prior art or are specifically set forth in the up ended claims.

I claim as my invention:

1. The combination with a ih'requenrychanger of the commutator type or armature means including! brushes in electrical quadrature with the main brushes for producin r, such commutating field. therein as to substantially neutralize the elect-rmnotive force in the short-circuited armature ioils undergoing commutation.

2. The con'ibination with a frequencychanger ot' the commutator type. of armature means for producing a commutating held to be cut by the slim-t-circuited armaturc coils undergoing; connnutation said. means being energized. by current oi? the frequency lowing through the main commutator oil the machine.

3. In a trequency-cluinger oi? the commutator type, the combination with an armature provided with a main winding and with. a main cou'imutator and slip rings associated therewith :tor the supply and removal of current to and from the armature winding", respectively. oi an auxiliary distributed winding on said arn'iaturc, and means for supplying said. distrfbiited winding: with aiternating current of the frequency flowing through the main commutator in such. manner that a commutatingr field is produced in said auxiliary winding, and operative upon the short-oircuitedv armature coils of said main winding; undergoing: commutation.

4. in a frequcncy-ehanger oi the commutator type the combination with an armature provided with a. main winding and with a main commutator and slip rings sociated therewith for the supply and removal of current to and. from the armature winding, respectively. oi an. auxiliary distributed winding on said armature. an auxiliary commutator associated tl erewith, brushes on said commutator in electrical quadrature to the main brushes oi. the machine and means for supplying current to said auxiliary brushes ot the 'l'requency of the current lowing through the main commutator ot the machine.

5. In a, trequency-changrer of the commutator type. the combination with an. armature provided with a main winding and with a main counnutator and slip rings 2. sociated therewith tor the supply and removal of current to and. from the armature winding, respectively, oi an auxiliary distributed winding on said armature. an auxiliary commutator associated therewith, brushes on said commutator in electrical quadrature to the mam brushes oi" the ma- I said chine, and connections from the main ln'ushes or said. machine to said auxiliary brushes. whereby said auxiliary winding is energized with current at the frequency of the currents flowing; through the main romniutator oi? said machine. and a conmnrtating' hold is produced therein oi v such phase and u'iagnitnde as to radically in'iprove the commiu'ation of said machine.

6. The method oi improving commutation in a frequency-Changer ot the commutator type which comprises generating an altcrnating commntating field therein in electrical. (piadrature lo the main brus es and. oi the frequency ol the currents flowing through the main brushes.

7. The method at improving crnninul'ation. in. a -lircquency-changrcr or the commutator type provided with an auxiliary distriluitcd armature \Vll'ltllllQ which compri es supply inn currents of the frequency oil the urrents in the main commutator 0t said machine to points in said. auxiliary windinp in electrical qi'iadrature to the main brushes of the machine.

8. The combination with a supply system embodying current of one frequency, of a load s steu'i demanding current of diitercnt i'requency from that of? said supply system, and a treiuiency-changer therebetween comprising an armature provided with a main counnutator and slip rings associated respectively with a main armature winding. one oi? said LljllltllilQ-tl'fiIiSii'ilttlTlQj means being connected to said supply circuit and the other to said load circuit.. means tor complotting a magnetic circuit ilor magnetomotire forces produced in said armature by said main winding, an auxiliary armature winding on said armature, an auxiliary commutator associated tl'ierewith, brushes bearin on said auxiliary commutator in electrical quadrature to the main brushes of the machine, leads connecting; said auxiliary brushes with said main brushes respectively, whereby said auxiliary armature winding is energized, with. currents at the frequency of the currents flowing through. the main commutator and a commutatiugr hold is produced therein oi? such frequency. phase and. magnitude to compensate tor the sparking; elecirmnotive lor es in the short-circuited. main armature coils undergoing: commutation, and means for driving, said armature a t any desired speed.

9. The method of operating a system embodying; a supply cirmiit of one frequency, a load. circuit oil another frequency and a driven armature connected tl'ierebetween and provided with main and. auxiliary distributed, windings. with main coi'innutator and slip rings conductirely associated with said main winding' and with an auxiliary commutato'r conductively associated with auxiliary armature winding which comprises supplying currents to said auxiliary winding at points in quadrature to the maincommutator brushes and of the frequency of the currents flowing through commutation.

10. The combination with a frequency changer having an armature member and a commutator-type armature winding on said armature member, of main brushes bearing on the commutator member of said armature winding for connection with an alternatingcurrent system of one frequency, and means excited from said main brushes and including auxiliary commutator brushes associated with said armature member and displaced approximately 90 electrical degrees from said main brushes for producing a commutating field.

11. The combination with a double-current machine of the type having an armature member provided with sliprings, a main commutator member and a pair of main brushes bearing on said main commutator member, of auxiliary means for producing a commutating field and including an armature winding separate from the winding associated with said main commutator member, an auxiliary commutator member associated with said separatewinding, and auxiliary brushes bearing on said auxiliary commutator member.

In testimony whereof, I have hereunto subscribed my name this 30th day of Aug. 1919.

CHARLES LEG. FORTESGUE. 

